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RE: [Xen-devel] 3.0.2-testing: pci_set_dma_mask, pci_set_consistent_dma_

To: "Tom Hibbert" <tom.xen@xxxxxxxxxxxxxxxxxxx>, <xen-devel@xxxxxxxxxxxxxxxxxxx>
Subject: RE: [Xen-devel] 3.0.2-testing: pci_set_dma_mask, pci_set_consistent_dma_mask(pci, 0x0fffffff) returns < 0 (ICE1712)
From: "Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>
Date: Wed, 12 Apr 2006 13:14:28 +0100
Delivery-date: Wed, 12 Apr 2006 05:14:55 -0700
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Thread-topic: [Xen-devel] 3.0.2-testing: pci_set_dma_mask, pci_set_consistent_dma_mask(pci, 0x0fffffff) returns < 0 (ICE1712)
>         /* check, if we can restrict PCI DMA transfers to 28 bits */
>         if (pci_set_dma_mask(pci, 0x0fffffff) < 0 ||
>             pci_set_consistent_dma_mask(pci, 0x0fffffff) < 0) {
>                 snd_printk(KERN_ERR "architecture does not 
> support 28bit PCI busmaster DMA\n");
>                 pci_disable_device(pci);
>                 return -ENXIO;
>         }
> I commented it out, and the module loaded but I got a burst 
> of static from the speakers. I suspect that this code is 
> incompatible with Xen.
> Why does Xen not allow the dom0 to set these parameters? My 
> development workstation is my main home box, and I like to 
> have sound on it.

Xen's allocator currently only supports a 31 bit DMA zone, which is
sufficient for the vast majority of hardware devices. I guess you could
try hacking the constants, but you might exhaust a 28b pool.


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